Various methods are known as a method for producing fluorinated halogenated hydrocarbons, which are used as blowing agents, cleaning agents, refrigerants, etc. In most of these methods, halocarbons or halogenated hydrocarbons are used as a starting material, and are highly fluorinated by fluorination or a hydrogen fluoride (HF) addition reaction.
In this case, as a method for fluorinating halocarbons or halogenated hydrocarbons, a method in which halocarbons or halogenated hydrocarbons as a starting material are reacted with HF is known (Patent Literature 1). As a specific method, there is, for example, a method in which halocarbons or halogenated hydrocarbons as a starting material and hydrogen fluoride (HF) are supplied to a reactor packed with a catalyst, and subjected to fluorination treatment to obtain a highly fluorinated halogenated hydrocarbon.
With regard to a method for producing CF3CCl═CH2 (HCFO-1233xf), for example, among these methods, various methods have been reported. A method has been reported in which CCl3CHClCH2Cl (HCC-240 db) is used as a starting material, and hydrogen fluoride (HF) is supplied in an amount exceeding the stoichiometric amount and reacted with the starting material (Patent Literature 2).
In this method, an outflow obtained from a reactor is a mixture containing not only the desired product, i.e., HCFO-1233xf, but also an equimolar or excess amount of HF relative to HCFO-1233xf. Furthermore, this product also contains, in addition to unreacted starting material HCC-240 db, other hydrochlorofluorocarbons as intermediates. To purify and use chlorinated hydrocarbons such as hydrochlorofluorocarbons including HCFO-1233xf, and starting material HCC-240 db from such a mixture, it is necessary to remove HF contained in the product. As a method therefor, a method in which a mixture containing chlorinated hydrocarbons and HF is treated with water or an alkali aqueous solution to absorb HF can be used. However, this method requires a large amount of water or alkali solution, resulting in the discharge of a large amount of industrial wastewater. It is thus undesirable in terms of environmental protection and production costs.
In addition, as another method for removing HF, there is a method in which HF is reacted with H2SO4 to collect HF as hydrofluoric-sulfuric acid. This method can be applied to removal of HF from a mixture of one or more chlorinated hydrocarbons and HF. However, in this method, the produced hydrofluoric-sulfuric acid is highly corrosive, and thus the materials of devices to be used are limited to highly corrosion-resistant materials. This leads to an increase in production costs.
Furthermore, in the case of the above method for removing HF, advanced technology is required to reuse the removed HF for a reaction. This leads to an increase in production costs even when the collected HF is recycled.